Wannier two-electron ionization ladder of 1P degrees symmetry in H-, He, and Li+

We have developed a systematic approach for identifying a priori and computing accurately wave functions of a special class of doubly excited states which seem to lead in a regular way to the Wannier state at the two-electron ionization threshold. As an application, we present a variety of new and experimentally verifiable results for the $^{1}\mathrm{\ifmmode^\circ\else\textdegree\fi{}}$ symmetry in ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$, He, and ${\mathrm{Li}}^{+}$.